Multistage telescopic hoist

ABSTRACT

A multistage telescopic hoist operable by pressurized compressible fluid is provided with an internal check valve and hollow probe mechanism associated with a tubular base section and at least a lowermost tubular section telescopically contained within the base section to provide lowering of the hoist without oscillation tendency.

United States Patent Sherman W. Bushnell, Jr. 1213 East Cherry St.,Wash. 770,310

Oct. 24, 1968 Jan. 5, 1971 Inventor Appl. No. Filed Patented MULTISTAGETELESCOPIC HOIST 4 Claims, 3 Drawirg Figs.

U.S. Cl 91/168, 91/451, 91/422 1nt.Cl FlSb 11/18 Field of Search 91/168,

45 1 (cursory); 92/5 1--53(cursory) [56] References Cited UNITED STATESPATENTS 2,257,324 9/1941 Behm et a1 91/168 2,872,904 2/1959 Van DenBeemt 91/168 FORElGN PATENTS 877,869 9/1961 ireat Britain 91/168 PrimaryExaminerPaul E. Maslousky A!t0rneySeed, Berry & Dowrey ABSTRACT: Amultistage telescopic hoist operable by pressurized compressible fluidis provided with an internal check valve and hollow probe mechanismassociated with a tubular base section and at least a lowermost tubularsection telescopically contained within the base section to providelowering of the hoist without oscillation tendency.

PATENTED m 5 m1 3552.267

I'NVENTOR.

AT TORNEYS SHERMAN W. BUSHNELL JR.

more particularly, is of the specialized type in which the lowest stageof largest diameter raisesand retracts first rather than'having theuppermost stage of smallestdiameter be the first to extend and retract.

When such a hoist is used for raising loads such as ducts, installation,ceiling boards, etc: for a'workman to a given height,

it isnormally preferred to have the hoist retract as rapidly as possibleafter the load has been removed. In certain instances it isadvantageous-to beable, to adjust the height of the load with precision.When such adjustment requires a lowering of the hoist by a dumping offluid a relatively slow discharge rate is required in order toadequatelycontrol the descent rate whereas when it is desired to rapidly'lower thehoist under a no-load condition to pickup another load a quick dischargeof the fluid is required. The present invention aims to provide improvedmeans for dumping the hoist at both slow and fast discharge rates tofulfill the described performance requirements. and to do so in anunusually simple and economical manner. v

The invention also aims to provide lowering of the hoist 3 withoutshattering or oscillating tendencies being encouncombination of partshereinafter described and claimed.

' FlG. 1 is a perspective of a partially "extended telescopic hoist; i 3

HO. 2 is a vertical crossjsectiondetail of the hoist of this invention;and 1 FIG. 3 is a cross section taken along the line 3-'-3 of FIG. 2

In brief, the invention comprises a plurality of telescopic cylindersprovided with a compressible pressurized fluid. The intermediatecylinders are closed at their lower ends and the uppermost cylinder andintermediate cylinders serving as pistons to lift the cylindersresponsive to the introduction-of pressurized fluid into the basecylinder. The pistons of the intermediate cylinders have center openingstherethrough for the passage of fluid from one cylinder to the next. Atleast the lowermost of the intermediate cylinders is provided with acheck valve which closes the pistonopening. The check valve may take theform of a weighted ball adapted to be lifted from its seaton the piston,when the cylinder is retracted, by a vertical probe mounted in the baseof the base cylinder. The probe is hollowand connected to a dischargevalve for rapid lowering of the hoist, and also has adequate clearancewith respect to the piston opening to permit a throttled flow of air ineither section 14, a plurality of tubular intermediate sections 15, and

an elongated tubular upper section 16 telescopically contained one inanother with the base section having the largest diameter and the uppersection having the smallest diameter. All of these sections may becylindrical. The hoist fits into spaced sockets 17, 18 presented by thetripod unit 12 and a pressure tank 19-is carried by means of a mountingbracket attached to the tripod. The tank 19 contains a suitable fluidsuch as carbon'dioxide under pressure and has suitable pressureregulators and gauges. Flexible hoses 21 transfer fluid to and from thebase of the hoist through a handheld manually operable flow controlvalve assembly connected to the manifold and the hoist via lengths offlexible hose 21. The valve assembly 20 is a three-way valve by whichpressure fluid from the tank can be directed to' the hoist or fluid canbe dumped from the hoist to the atmosphere. ln addition both such flowscan be shut off. The base section of the hoist is closed at itsdirection through the piston opening when pressurized fluid is suppliedor dumped from the bottom cylinder. If desired,

more than one of the intermediate cylinder pistons may be provided withcheck valves and the probe length extended lower end by an annular .baseplate 22 containing porting for the su )ply and discharge of the gasfromthe tank. This porting includes a vertical center passage 23 whichextends downwardly from the upper face of the plate to a radial passage23' connecting by an external elbow 24 to an exhaust valve unit 25. Asecond vertical passage 26 radially offset from the first, also connectswith a radial passage 26' to the outside whereat a fitting connects tothe'hose 21. The valve assembly 25 has its valve 27 seated at 28' by acompression spring sleeved on the valve stem 31. Manual unseating of thevalve to exhaust from the hoist through port 32 is performed by swinginga toggle 33 pivoted to the stern in opposition to the spring 30. Thevalve unit 25 also serves as a pressure relief valve since it willunseat in response to a predetermined pressure in the hoist. Theintermediate sections 15 of the hoist are of similar const'ructionexcept for diameter and each is closed at its lower end by steppedpiston 34 having a peripheral ceiling gasket 36 in sliding contactwiththe inner wall of the next lower section of the hoist. The pistons areeach connected to its respective tubular section by an inwardlyextending annulus 35 roll formed in the section which fits into acircumferential groove formed in the piston. An elastic O-ring 37 isprovided near the top of each piston and a cylindrical spacer sleeve 38is located between each of the tubular sections and abuts as an upperlimit against a rib 40 roll formed at the upper end of each section tolimit the degree of extension of the hoist sections relative to oneanother. I

Each of the pistons 34 of the intermediate sections 15 are formed withan upper well 41 having a tapered bottom wall 42 which merges with anaxial bore 43 continuing downwardly through the piston. Carried in thewells are respective weighted balls 44 larger in diameter than the axialbores 43 to serve as check valves when the respective stage of the hoistis extended. As part of the present invention a center probe 45 is pressfitted into the center bore 23 of the base plate and projects upwardly adistance approximating the combined thicknesses of the pistons of theintermediate sections. This provide a passage 46 around the probe fromone section of the check valves close to isolate the'cylinders from oneanother.

Referring to the drawings, the present invention is illustrated appliedto a hoist 10 carrying at the top a load support I ing assembly andmounted on a collapsible tripod assembly 12. The hoist assemblycomprises an elongated tubular base hoist to another when the probeextends through the axial center bores 43. Such gas flows into or out ofthe hoist through theoffset vertical passage 26 and radial bore 26 andvia the flexible hose 21 to the hand control valve 20. From this valve afurther length of the base 21 connects with the tank 19.

When the hoist sections are all completely collapsed, their pistons restone upon another on the base section 22 as shown in FIG. 2 and the probe45 extends upwardly through all of the distance of the intermediatesections. In this position the 7 probe displaces all-of the check valveballs so that there is communication from one hoist section up to theother in the space around the probe within the vertical bores.

' To raise the hoist from this position the hand control valve is setsuch as to feed pressurized gas from the container through the hose andpassages in the base section up into the space between the base sectionand, the lowermost piston. Since .the bottom area of this piston isgreater than the pistons of the other sections, the lower hoist sectionmoves upwardly first and continues'if the supply of pressurized fluid iscontinued, until the lower piston is fully extended at which time theprobe will be fully withdrawn from all of the pistons. The pressurizedgas then liftsthe check valve ball in the first cylinder from its seatpermitting the flow of the gas in the space between the first and secondpistons thereby causing the second cylinder to rise upwardly relative tothe first and if the flow of gas is continued from the tank, the secondcylinder continues upwardly until it is further extended and then thenext higher check valve opens and the process continues until thedesired hoist height has been achieved. At this point the supply of gasis cut off at the hand control set and the balls then settle into theirseats and isolate each cylinder from the other.

1 From this time on, upward height adjustmentcan be .made

by transferring'fluid to or from the hoist cylinder, by use of the handcontrol valve. When it is desired to have an upward adjustment,'theinflowing air unseats all the check valves and then causes the nexthighest nonfully extended section of the hoist to rise accordingly. Onthe other hand, if the adjustment is to be downward, venting at thehand'control set causes the discharge of gas from the base section onlyand hence causes the adjustment to occur in the area o'f largestcrosssection as is preferred to permit a fine-adjustment. I

When it is desired to speedily retract the hoist as when the load hasbeen removed and a new load is to be applied, the operator, instead ofusing a handv setfor venting, merelylifts the handle of the check valveat the base of the hoist. As a result, the air is quickly ventedthrough'the center of the probe on the base section and then whenthe'first piston reaches the base the probe unseats its check valve balland vents the space between the first and the second pistons. When thisisaccomplished, the next ball up is unseated by the probe and thiscontimes until allofthe balls have been 'unseated and all 'of thechambers have been ventedthroughthe relief valve. FIG, 1' illustratesthe parts in the condition after the bottom two'cylindrical sectionshave been vented when the next higher section is in the process of beingvented through the probe.

The clearance between the outside of the probe and the boresand thepistons is made such that the flow capacity of thespace is no greaterthan that of the hose and out through the hand valve. This is done sothat the lower piston will not oscillate or chatter at the point ofun'seating of the lower ball byv the probe. If this were not so the highpressure fluid above the probe would flow into the lowermost chamberabove the base plate and cause the lowermost piston to raise therebyagain shutting off the lower check valve. Then when additional ventingof the lower chamber had continued the ball would again be raised'by.the probe and the same action repeated, possibly several? times beforethe desired degree of venting has'been achieved. i 2

ll it is desired to automatically restrict the upward expansion of thehoist assembly. toa predetermined height. the handle on thepressurerelief valve can be connectedasby a string to the top of thehoist so. that when the string is taut the handle is lifted and thepressure reliefi valve dumped, ,i, s I

It is thus seen that the-hand set is used tom ng'.the hoistpr for minuteadjustment thereof, and that'wher rt 'sadjustrnent is downward thecontraction '.is .taken ,by t lowermost cylinder first. It is; -alsothat-when'it f :desired to qui ckly lower the cylinderjtheprgssurerelief valve is opened and-the upper cylinder lowers first; .1 y,1 f s in many applications, th fi neadjustment providedbythe ball checkvalves will not be requiredover the full height range of the hOlSL-ii'tsuch applications, a single ball valvepositioned in.the well 41 of thelowermost ij termediate cylinder will provide the necessary ine"hig& tadjustment. Thus, probe 45 need only be of a ength su cient to extendthrough the piston of the lowermost 'interriiediate cylinder.

l. A multistage telescopic hoistrcofnprising a plurality of elongatedconcentric telescopically associated, tubular sections of progressivelysmallercross section? closed at itslower end, a top section of thesmallest cross section'iclosed atone'of its'end, and a bottomintermediate section-=having a piston on its lower end slidably' mountedin a base section and having an openingtherethroughja hollow probe oflessjouter-diar'neter than the diameter of 'the"opning,-allowin'g fli'idcommunication therebetween mounted near the lower end of theZbasesection and projecting upwardly lengthwise of the base section inalignment with said opening to extend therethrough but not I seal theopening when said intermediate section is-retracted,

ball check valve means adapted to closez'said piston openingwhensaidpiston isabove the probe and adapted to be opened by the probewhensaidinterrnediate' section is retracted, pressurized fluid supplycontrol means communicating withtth'e bottom side of said piston througha'bo re in the lowertend of said base section for extending andretracting the hoist and dump valve means communicating with theinterior of the probe through a bore in the lower end of said basesection for rapidly ventingwfluids from the hoist.

2. The hoist of claim 1 including at least one other intermediatetubul'ar sectionhavinga piston a t-its lower end with an unobstructedopening theret-hrough the piston of said other intermediatesection-being adapted to seat on the piston of the first-namedintermediate'section when retracted. t-

3. The hoist of clairn 1 wherein the relative diameters between theprobe the piston opening are such that they will provide a restrictedexhaust flow of the fluid.

4. The hoist of claim 1 and further including a concentric contiguoussleeve surrounding the'exterior portionof each of the tubular sectionsadapted to abut the piston ofitssect'ion and an inwardly projectingshoulder of the tubular section having the next larger cross-sectionalarea whereby extension of each sleeve is limited] I T the

1. A multistage telescopic hoist comprising a plurality of elongatedconcentric telescopically associated tubular sections of progressivelysmaller cross section, closed at its lower end, a top section of thesmallest cross section closed at one of its end, and a bottomintermediate section having a piston on its lower end slidably mountedin a base section and having an opening therethrough, a hollow probe ofless outer diameter than the diameter of the opening, allowing fluidcommunication therebetween mounted near the lower end of the basesection and projecting upwardly lengthwise of the base section inalignment with said opening to extend therethrough but not seal theopening when said intermediate section is retracted, ball check valvemeans adapted to close said piston opening when said piston is above theprobe and adapted to be opened by the probe when said intermediatesection is retracted, pressurized fluid supply control meanscommunicating with the bottom side of said piston through a bore in thelower end of said base section for extending and retracting the hoistand dump valve means communicating with the interior of the probethrough a bore in the lower end of said base section for rapidly ventingfluids from the hoist.
 2. The hoist of claim 1 including at least oneother intermediate tubular section having a piston at its lower end withan unobstructed opening therethrough the piston of said otherintermediate section being adapted to seat on the piston of thefirst-named intermediate section when retracted.
 3. The hoist of claim 1wherein the relative diameters between the probe and the piston openingare such that they will provide a restricted exhaust flow of the fluid.4. The hoist of claim 1 and further including a concentric contiguoussleeve surrounding the exterior portion of each of the tubular sectionsadapted to abut the piston of its section and an inwardly projectingshoulder of the tubular section having the next larger cross-sectionalarea whereby extension of each sleeve is limited.